Brake Booster Restoration

[ADDvanced]

Alright, kind of dumb question but this is new territory for me so I figured I'd ping the hive mind.

I'm in the middle of replacing my master cylinder (77 911) due to leaking; it leaked brake fluid into the booster itself and wrecked the paint on it; I scuffed/sanded the exterior, and then washed out the inside of the booster with dawn/water. However, there's still rust INSIDE the booster.

Is this one of those things where if I can just paint it and not think about it again, or will having some rust inside the booster come back to bite me in the ass? I know there shouldn't be fluid in there... just wondering if a bit of rust dust inside the booster would cause any issues or if I should just send it.

[gsxrken]

Try giving these guys a call and see what they say. I’ve had them do two boosters for me over the years, although they were not Porsche. I don’t know if they restore Porsche ones, but they would probably be able to comment on your question. From my limited understanding, leaking master cylinders into the booster is the death knell for a booster, but I imagine it is time sensitive.
https://www.powerbrakebooster.com/

[jess p]

Through advanced auto it is $800 to rebuild it and you won’t see it for a month I’m told. I have the same problem with my 82 sc, however, the car has sat for many years while I’ve waited to restore it. My plan is to replace the pedal assembly with a 76 and install an older mc.

[Locker537]

Here's another booster service company that has come recommended to me in the past: Home - KARPS POWER BRAKE SERVICE & CYLINDER SLEEVING

[ADDvanced]

I wound up just sanding and painting it. There's a little rust inside but I'm just going to ignore it.

[pampadori]

Cost from Advance Auto to send it off to Cardone for rebuilding is $130 and might take a few weeks. They pop the them apart, media blast it, replace the internal bits and seals and send it back to you unpainted.

[PeteKz]

ADDvanced: As long as the sealing surfaces were cleaned and repainted and it holds vacuum, it doesn't matter whether there's surface rust inside. Even a concours judge would be hard pressed to find that!

[7783911]

What is best way to test the booster (ie vacuum hold)?

[Marc Bixen]

+1 for Karps. They just did a 77 930 for us a few months ago.

[LJ851]

Originally Posted by pampadori

Cost from Advance Auto to send it off to Cardone for rebuilding is $130 and might take a few weeks. They pop the them apart, media blast it, replace the internal bits and seals and send it back to you unpainted.

FWIW, when I received my booster back from Advance Auto it was painted silver. It was a color extremely similar to blasted steel and I didn’t even realize it was painted until I was prepping it to paint satin black.

My costs match pampadori, not the $800 mentioned earlier in this thread.

[7783911]

I will test vacuum and if needed, use Cardone direct if possible

[pampadori]

@7783911 i took video of my endeavors:
https://www.youtube.com/watch?v=SQWrxsmZBkA

After getting the part back:
https://www.youtube.com/watch?v=bG72UAuEnNM

[7783911]

If I want to test my check valve on the booster can I use a vacuum tested (MityVac) on the check valve?

[PeteKz]

Yes. That should work, but a Mityvac doesn't have a long stroke to its plunger, so you will probably wear out your hand pumping it down.

[7783911]

pump away .... fun wow